The present invention relates generally to a control system for an engine of an automotive vehicle, and more particularly to a method and apparatus for controlling an operational position of a throttle valve in the engine.
Electronic engine controllers have used position sensors for closed loop control of throttle valves. A desired resolution for the position sensor depends on the specific application of the sensor. Also for a particular application the desired resolution may vary throughout a desired position sensing range. For example, the preferred resolution for the throttle position sensor may be higher at lower position angles (near a closed position) versus higher position angles. Typically, a position sensor has an output signal defined by a transfer function with different slopes is preferred for sensor fault detection.
Traditionally, throttle positions sensors have output signals defined by linear transfer functions. An engine controller uses the linear transfer function characteristic to determine an operational position of a throttle valve based on the output signal. Unfortunately, the position sensors, having a single sloped linear transfer function, have a relatively equivalent resolution over the entire range of operation which may be undesirable for throttle valve applications.
Further, some electronic controllers utilize multiple slope linear transfer functions to map a throttle position sensor voltage to a throttle position. The multiple slope linear transfer functions allow for a varying position resolution over the position sensing range that may be desired for throttle valve applications. However, each of these multiple slope linear transfer functions have a breakpoint which is a point where two line segments with different slopes meet. As a result, position measurement of throttle valve near these breakpoints may result in position measurement errors.
The inventors herein have recognized that it would be desirable to have a position control system with increased resolution in important operational regions of interest that is simpler to implement and more accurate than known methods.
The foregoing and advantages thereof are provided by a method and apparatus for controlling an operational position of a throttle valve in an engine. The system includes a position sensor operably connected to the throttle valve that generates a first signal. A controller is operably connected to the position sensor. The controller is configured to determine a current position of the throttle valve using a transfer function defining a curve with no breakpoints and the signal from the position sensor. The controller is further configured to change the operational position of the throttle valve based on the current position and a desired position of the throttle valve.
One of several advantages of the present invention is that it provides an improved method of determining a position of a device, with increased accuracy, due to increased resolution in a range where more resolution is desired.
Additionally, the present invention provides increased resolution in a control system that has manufacturing and interpreting ease equal to or better than traditional control systems.
Furthermore, the present invention provides several alternatives that have different varying slope conversion characteristics as to satisfy various different applications.
The present invention itself, together with attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying figures.